Flexible coupling

ABSTRACT

A lightweight, flexible coupling is provided by the present invention for transmitting torque and accommodating axial and angular misalignment between drive and driven shafts. The coupling includes at least one reinforcing ring disposed between a pair of hubs or plates having projecting pins to which are secured elongated filaments that are coated or impregnated with a flexible matrix. The filaments are wrapped from the hub or plate on one side of the reinforcing rings(s), to and across the reinforcing rings(s) and then to the hub or plate on the opposite side of the reinforcing ring(s) following a geodesic path. Torque applied to the coupling is thus transmitted between the hubs or plates solely through the filaments.

This is a division of application Ser. No. 181,260 filed Aug. 25, 1980,now U.S. Pat. No. 4,391,594.

FIELD OF THE INVENTION

This invention relates to the field of couplings, and, morespecifically, to a light weight composite coupling capable of carryinghigh torsional loads while accommodating relatively large angular andaxial misalignment between adjoining shafts.

BACKGROUND OF THE INVENTION

The basic requirements for any connection used to couple adjoiningshafts include adequate torque carrying capability for the particularapplication and sufficient flexibility to accommodate at least limitedangular and axial misalignment between the shafts to be joined. In aneffort to achieve the combination of torsional stiffness and angular andaxial flexibility, many early coupling designs reduced the thickness ofsolid metal members, bearings, gear teeth and the like to obtain greaterresiliency and thus flexibility. However, high fabrication costs and theinevitable wear generated by constant rolling or sliding contact of theparts in such couplings reduce their utility and cost effectiveness.Moreover, it has been found that where sliding parts are involved,concentricity between the drive and driven shafts to be coupled isdifficult to maintain due to the clearance required between the parts,which further reduces their utility in many applications.

SUMMARY OF THE INVENTION

The recent development of composites, which consist of a plurality offiber strands impregnated or coated with a matrix material, is ofparticular value in the construction of universal joints, flywheels andflexible couplings. See for example U.S. Pat. Nos. 3,977,273 to Ernst etal and 4,116,018 to Weible. As disclosed herein, by eliminating the thinflexible metal members of prior art connectors and utilizing a layer orlayers of composite material, a lightweight flexible connection isprovided by the subject invention which is torsionally stiff and at thesame time can accommodate much higher angular and axial misalignmentthan prior art connectors. The flexible coupling herein includes anouter reinforcing ring disposed between a pair of hubs or plates oflesser diameter, each having a central bore or a shaft extension, whichare concentrically disposed on either side of the reinforcing ring. Anelongated fiber strand or bundle, impregnated or coated with a flexiblematrix such as natural rubber or urethane, is continuously wrapped froma point tangent to the central bore or shaft of one hub, to the outersurface of the reinforcing ring and then to a corresponding point on theother hub following a geodesic path. As described below, wrapping thecontinuous fiber strand or bundle in this manner will be considered forpurposes of discussion as forming a plurality of individual fibers orstrands. Since the only connection between the hubs is by theirattachment to the fibers, torque from the driving shaft is transmitteddirectly through the fibers to the driven shaft, placing each fiber intension. The flexible matrix with which the fibers are impregnated orcoated enables adjacent fibers to move angularly and axially withrespect to one another to accommodate angular and axial misalignmentbetween the drivers and driving shafts. As discussed in detail below,the number and configuration of the reinforcing ring(s) may be alteredto obtain desired performance, and several means may be utilized toenhance anchoring of the fibers to the hubs or plates on each side ofthe reinforcing ring.

Therefore it is an object of the present invention to provide a lightweight flexible coupling capable of carrying high torque loads whileaccommodating axial and angular misalignment between adjoining shafts.

It is another object of the present invention to provide a flexiblecoupling including at least one reinforcing ring disposed between a pairof hubs or plates of lesser diameter which are concentric with thereinforcing ring.

1t is still another object of the present invention to provide aflexible coupling having a reinforcing ring disposed in spaced relationbetween a pair of hubs or plates, wherein an elongated fiber strand,coated or impregnated with a flexible matrix, is wrapped from a hub orplate on one side of the reinforcing ring, to and across the reinforcingring and then to the hub or plate on the opposite side of thereinforcing ring in a geodesic path.

It is a further object of the present invention to provide anchoringmeans for securing the fibers to the hub or plate on opposite sides ofthe reinforcing ring.

DESCRIPTION OF THE DRAWINGS

Objects in addition to the foregoing will become apparent uponconsideration of the following discussion taken in conjunction with theaccompanying drawings wherein:

FIG. 1 is an isometric view of one embodiment of the composite couplingof the present invention.

FIG. 2A is a cross-sectional view taken generally along line 2A--2A ofFIG. 1.

FIG. 2B is a cross sectional view taken generally along line 2B--2B ofFIG. 1.

FIG. 3 is a partial isometric view of the coupling herein showing themanner of wrapping the fiber material from one side of the coupling tothe other.

FIG. 4 is a partial cross-sectional view of an alternative embodiment ofthe coupling of the present invention showing plural reinforcing rings.

FIG. 5 is a cross sectional view showing a pair of couplings inaccordance with the present invention connected by a shaft in acontinuous wrapping operation.

FIG. 6 is a front view of an alternate embodiment of the couplingherein.

FIG. 7 is a cross sectional view taken generally along line 7--7 of FIG.6, showing an embodiment of the fiber anchoring means of the presentinvention.

FIG. 8 is a cross sectional view of an alternate type of fiber anchoringmeans for the embodiment of the subject invention shown in FIG. 6.

FIG. 9 is a front view of another embodiment of the coupling herein witha still further type of fiber anchoring means.

FIG. 10 is a cross sectional view taken generally along line 10--10 ofFIG. 9.

FIG. 11 is a front view of still another embodiment of the couplingherein.

FIG. 12 is a cross sectional view taken generally along line 12--12 ofFIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and in particular to FIGS. 1, 2A and 2B,one embodiment of the composite coupling of the present invention isshown and labeled generally with the reference 11. Coupling 11 includesa pair of hubs 13 and 14 which are held in spaced relation andconcentric with one another by a removable mandrel 15. Each hub 13 and14 includes a nonaxisymmetric shaft extension 17 having a generallycircular flange 19 attached at one end in which a plurality of bores 21are drilled or machined at spaced intervals for attachment to the flangeof a shaft (not shown) to be coupled. The shaft 17 of hubs 13 and 14 ispreferably hexagonal in cross section as shown in FIG. 2B, but othernonaxisymmetric cross sections may be utilized for purposes to becomeapparent below. In addition, hubs 13 and 14 need not include a flange 19for attachment to a drive or load shaft, if in a particular applicationa key or spline connection between the hubs 13 and 14 and shafts ispreferred.

A reinforcing ring 23, of larger diameter than hubs 13 and 14, isdisposed between the hubs 13 and 14 and held in place by the outer edgeof mandrel 15. The reinforcing ring 23 and hubs 13 and 14 are preferablyformed of a lightweight metal or a graphite/epoxy composite havingsufficient compressive strength to resist the forces induced by thetorque of the anticipated application for coupling 11. At this point, itshould be noted that prior to the formation of coupling 11, discussedbelow, there is no direct connection between the hubs 13 and 14 eitherwith each other or with the reinforcing ring 23 except through themandrel 15 which is later removed. Relative movement of the hubs 13 and14, and in turn the shafts to which they are connected, is thuscompletely dependent on the connecting means attaching thereto.

Referring now to FIGS. 2A and 3, the connecting means for formingcoupling 11 is shown. A continuous length of high strength fiber strandsor bundles such as graphite, aramid, glass or a suitable equivalent iswrapped on a substantially geodesic path from a point tangent to theshaft 17 of hub 13, to and across the outer surface of the reinforcingring 23 and then to a corresponding point tangent to the shaft 17 of hub14 on the opposite side of reinforcing ring 23. As shown in FIG. 3,chords drawn from the center 28 of shaft 17 to the points at which thefiber contacts the edges of reinforcing ring 23, form an angle 8 withthe fiber on either side of coupling 11. The following relationshipapplies in wrapping the continuous fiber along the geodesic or shortestpath between the shafts 17 of hubs 13 and 14:

    Sin θ=r/R

Where:

r=radius of the hub shafts

R =radius from the center of the hub shafts to the reinforcing ring

The significance of wrapping the fiber along the shortest or geodesicpath between the shafts 17 of hubs 13 and 14, is that application of atorsional force in the clockwise direction for example will beinstantaneously resisted by the tensile strength and modulus ofessentially one half of the fibers. The same torque carrying capabilityis provided for in counterclockwise rotation of coupling 11, wherein theother half of the fibers forming coupling 11 are placed in tension. Ifthe fiber did not follow the geodesic path, application of torque wouldcause a degree of slippage or straightening of the fiber since it is notmechanically attached to the reinforcing ring 23. This would result inunwanted torsional softness in coupling 11 and undesirable stresses inthe composite structure. Since the only connection between hubs 13 and 4is the fiber, all of the torque applied by the driving shaft will betransmitted directly through the fiber to the driven shaft andsufficient torsional strength must be provided to accommodate maximumtorque for a given application.

In forming the completed coupling 11, the continuous length of fiber isfirst coated or impregnated with a flexible matrix such as naturalrubber or urethane and then wrapped along the surface of mandrel 15 in ageodesic path as discussed above from hub 13 to reinforcing ring 23 andthen to hub 14. For purposes of discussion, each successive wrap of thefiber will be considered as forming an individual filament 27. Once awrapping circuit is completed, successive circuits lay down filaments 27immediately adjacent to one another to form a partial or completebladder or diaphragm 29 on either side of the reinforcing ring 23 whichincreases in thickness from the reinforcing ring 23 to the hubs 13 and14.

In the embodiment of FIGS. 1 and 2A the shafts 17 of hubs 13 and 14 arewrapped with a plurality of filaments 27, laid down side-by-side, ineach wrapping circuit. It has been found that with the application oftorque to coupling 11, a means of anchoring filaments 27 must beprovided to avoid slippage and unwinding. This has been a problem inmany prior art designs. The subject invention provides severalalternative anchoring means to avoid this limitation found in existingcouplings and universal joints as discussed below, and in thisembodiment the shafts 17 of hubs 13 and 14 are formed in anonaxisymmetric configuration to assure that filaments 27 are heldfirmly in place. Shafts 17 may be hexagonal as shown in FIG. 2B, butvarious other configurations are also utilized including octagonal orelliptic shapes.

A single layer of filaments 27 forming the diaphragms 29, and aplurality of layers of filaments 27 wrapped one on top of the otherabout shafts 17, is normally sufficient to provide the requisite torquecarrying capacity of coupling 11 while retaining sufficient flexibilityto accommodate axial and angular misalignment between the drive anddriven shafts to be connected. The number of layers of filaments 27 maybe increased as desired by simply repeating the wrapping process, withthe result being increased torque carrying capability but reducedflexibility of coupling 11. In addition, the filaments 27 may beoverwrapped by an additional layer of filaments 27 impregnated with arigid matrix material such as epoxy to rigidify diaphragms 29 and thefilaments 27 along shaft 17. In some applications it may be desirable toimpregnate filaments 27 along shaft 17 with epoxy for enhanced rigidity,while utilizing urethane or natural rubber impregnated filaments 27 fordiaphragms 29 to form a two matrix system. The characteristics ofcoupling 11 may also be altered by providing two or more reinforcingrings 23 as shown in FIG. 4, which increases the flexibility of coupling11 as compared to the configurations described above. Once the wrappingis completed, the matrix material is vulcanized while the coupling 11 isstill on the mandrel 15. The mandrel 15 may then be removed allowing thecured diaphragms 29 to flex freely.

Referring now to FIG. 5, a pair of couplings 11 of the type essentiallyidentical to that described above and shown in FIGS. 1 and 2A, areconnected by a drive shaft 31 formed in a continuous winding operation.Drive shaft 31 may be formed of a rigid cylindrical-shaped material oras an elongated extension of the hub shafts 17 of couplings 11, in whichcase filaments 27 coated or impregnated with the same flexible matrixmaterial (urethane or natural rubber) as that utilized for the couplings11 are wound directly from the couplings 11 to drive shaft 31. The rigidcylinder or elongated hub shafts 17 act as a reinforcing liner for driveshaft 31 to provide the necessary torque carrying capability. In thealternative, a removable mandrel (not shown) is disposed betweencoupling 11, and filaments 27 coated with a relatively stiff matrixmaterial such as epoxy are wrapped therealong. In this case, therigidity and torque carrying capability of the filaments 27 coated withepoxy to form drive shaft 31 is sufficient to avoid the use of areinforcing liner, but the filaments 27 forming diaphragms 29 ofcouplings 11 are still impregnated with a flexible matrix material toretain the desired axial and angular misalignment accommodationcapability.

It is contemplated that the coupling-shaft-coupling configuration ofFIG. 5 in which all of the filaments 27 are coated or impregnated with aflexible matrix material and a reinforcing liner is used to rigidifydrive shaft 31, may be easier and less costly to manufacture than thealternate configuration. However the coupling-shaft-couplingconfiguration in which a flexible matrix is used to impregnate thecoupling filaments and a rigid matrix is used to impregnate or coat thedrive shaft filaments, will provide a lighter combination which may berequired in other types of applications.

The concept of wrapping a continuous fiber along a geodesic path from apoint tangent to the shaft 17 of hub 13, over a reinforcing ring 23 andthen to a corresponding point on hub 14, may be extended to a secondembodiment of the subject invention in which a coupling 33 is formedwith a pair of inner plates 35 and 37 separated by a removable mandrel(not shown) about which a reinforcing ring 23 is circumferentiallydisposed as shown in FIG. 6. In this embodiment, the filaments 27 arewrapped from a point tangent to the central bore 39 of inner plate 35across the surface thereof to and across the reinforcing ring 23, andthen to a corresponding point tangent to the central bore 41 of innerplate 37 in a geodesic path. The wrapping procedure for coupling 33 isthe same as that for coupling 11 discussed above, except that no shaftentensions 17 are attached to inner plates 35 and 37 and the filaments27 are laid down directly on the surface thereof.

As discussed above, anchoring means must be provided for filaments 27 toresist slippage under load and avoid unwanted torsional softness.Without the nonaxisymmetric shaft extensions 17 which provide anchoringmeans in coupling 11, alternate means of anchoring filaments 27 areprovided in coupling 33 as shown in FIGS. 6-9. In FIG. 7, inner plates35 and 37 are stamped or otherwise formed in a wave-like configuration,and include a plurality of bores 43 drilled or punched at spacedintervals at a given radius from the centers thereof. A pair ofcorrespondingly shaped outer plates 45 and 47, formed to engage innerplates 35 and 37 respectively, are also provided and include a pluralityof bores 49 corresponding to bores 43 of inner plates 35 and 37. Oncethe inner plates 35 and 37 are covered with filaments 27 upon completionof the wrapping procedure, outer plates 45 and 47 are securely attachedto the inner plates 35 and 37 respectively by tightening bolts 51inserted through the aligning bores 43 and 49. The filaments 27 aretightly pressed between the inner and outer plates on both sides ofcoupling 33 and tend to assume the wave-like shape of their surfaces.This provides a secure anchorage of filaments 27 under torque loads.

The same effect described above may be achieved with an alternateconfiguration of inner plates 35 and 37 and outer plates 45 and 47 asshown in FIG. 8. In this embodiment, a series of raised sections 53 aredisposed at spaced intervals about the surfaces of inner plates 35 and37 over which filaments 27 are wrapped. Correspondingly shaped raisedsections 55, formed on outer plates 45 and 47, are positioned such thatupon bolting the plates together the raised sections 53 of inner plates35 and 37 interlock with the raised sections 55 of outer plates 45 and47. The alternating raised sections 53 and 55 force filaments 27 toassume a wave-like configuration, as in FIG. 7, and securely anchor themin position.

Referring now to FIGS. 9-12, a third embodiment of the present inventionis shown wherein still further means of anchoring filaments 27 to avoidslippage is provided. A pair of hubs 57 and 59, each having an inwardlyfacing flange 58 and 66 respectively, are spaced apart by a removablemandrel (not shown) about which a reinforcing ring 23 of larger diameteris circumferentially disposed. In FIG. 10, hubs 57 and 59 include sevenpins 61 each having an outwardly extending flange 63, which are disposedat selected intervals on the surface of flanges 58 and 66 respectivelyat a constant radius from the central bore 65 of hubs 57 and 59.Filaments 27 are wrapped from a pin 61 of hub 57, to and across thesurface of reinforcing ring 23 and then to a corresponding pin 61 of hub59 following the geodesic path to form a coupling labeled with thereference 60. The winding is continued between the same two pins 61 ofhubs 57 and 59 until enough filaments 27 are laid down to obtain thedesired torsional strength, at which time the winding is transferred toa second set of two pins 61 and so on. Anchoring of the filaments 27 topins 61 is accomplished by the pin flanges 63 which prevent outwardradial or lateral movement.

The coupling 60 of FIGS. 9 and 10 is exceedingly light in weight andexhibits high torsional stiffness and strength in the direction ofwinding of filaments 27. It should be understood that the use offourteen pins 61 in coupling 60 is not critical and may be varied asdesired. By wrapping filaments 27 about pins 61 in one direction, hightorsional stiffness and strength are obtained only in that direction.This may be entirely satisfactory in many applications. However, inapplications where torsional strength is required for both clockwise andcounterclockwise rotation, the coupling 60 would not be appropriatesince filaments 27 would tend to unwind in one direction of rotation.

To avoid this limitation, the coupling 60 of FIGS. 9 and 10 may bemodified by replacing the flanged pins 61 with pins 64 having an outerspool 67 and an inner spool 69 to permit winding of filaments 27 inopposite directions from a single pin 64. In this embodiment of thesubject invention, shown in FIGS. 11 and 12, a modified coupling 62 isformed by continuously wrapping a set of three pins 64; one pin 64 beinglocated on the flange 58 of hub 57 and the other two pins being disposedat selected locations on the flange 60 of hub 59. The filaments 27 arefirst wound along the geodesic path from the inner spool 69 of pin 64 onhub 57 to the inner spool 69 of pin 64 on hub 59 until the desiredtorsional strength is obtained. The filaments 27 are then wound from theouter spool 67 of pin 64 on hub 57 to the corresponding outer spool 67of the second pin 64 on hub 59, until the desired torsional strength inthe reverse direction is obtained. The modified coupling 62 wrapped inthis manner is also relatively light in weight with the added capabilityof accommodating torsional loads in opposite directions. Moreover, thenumber of filaments 27 need not be the same in both directions where itis contemplated that the torsional loads in each direction will bedifferent.

Several improvements of the couplings herein over the prior art shouldbe noted. The continuous fiber is wrapped directly from one hub or plateto and across a reinforcing ring and then to the other hub or platealong the shortest possible or geodesic path. Since the hubs or platesare spaced apart, all of the torque applied to the couplings istransmitted through the fiber and resisted by the relatively hightensile strength and modulus of the fiber. The various anchoring meansdescribed above assure that the fiber remains in place under expectedoperating torque. Once the wrapping procedure is completed and themandrel removed, the cured filaments impregnated or coated with aflexible matrix such as natural rubber of urethane display a high degreeof flexibility in the angular and axial modes. The result is a lightweight coupling capable of transmitting high torque loads whileretaining sufficient flexibility to accommodate relatively high degreesof angular and axial misaligment between the shafts to be joined.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A coupling having a longitudinal axis fortransmitting torque and accommodating misalignment between a drivemember and a driven member comprising:at least one rigid reinforcingring encircling said axis; a pair of hubs spaced apart along saidlongitudinal axis and being disposed on opposite sides of and inconcentric relationship with said reinforcing ring, one of said hubsbeing attachable to said drive member and the other of said hubs beingattachable to said driven member; a plurality of pin elements fixedlymounted upon and projecting from each of said hubs, the direction ofprojection of said pin elements upon each of said hubs being away fromthe other of said hubs; a plurality of filaments individually coated orimpregnated with a matrix material, said filaments being wrapped in aplurality of wrapping circuits to form connecting means between saidhubs, said filaments in each of said wrapping circuits following ageodesic path and being wrapped between an associated pair of said pinelements, one pin element of each said pair being disposed upon said oneof said hubs and the other pin element being disposed upon said other ofsaid hubs, said filaments within each of said circuits being wrappedabout said one pin element of said associated pair and extending to andacross said reinforcing ring and then being wrapped about said other pinelement of said pair; each of said pin elements having anchoring meansintegral therewith for preventing displacement therefrom of filamentswrapped thereabout; whereby torque applied to said coupling istransmitted from said one of said hubs through said connecting means tosaid other of said hubs without significant slippage.
 2. A coupling asin claim 1, wherein said anchoring means includes a flange projectingoutwardly from the main body of each of said pin elements.
 3. A couplingas in claim 1, wherein at least one of said pin elements has a pair offilament receiving portions at spaced locations along the lengththereof, one of said filament receiving portions receiving thereonfilamentary material of one of said circuits and the other of saidfilament receiving portions receiving thereon filaments of another ofsaid circuits, said anchoring means of said one of said pin elementsincluding flanges respectively overlying and radially outwardly fromsaid filament receiving portions.